Apparatus for pulverized-fuel burning



E. LUNDGREN APPARATUS FOR PULVERIZED FUEL BURNING April 15; 1930.

Filed Noy. 50, 1923 INVENTOB wkfimunummm m Patented Apr. 15, 1930 I UNITED STATES PATENT OFFICE EDWlTN LUNDGREN, or EEEnEEIoK, MARYLAND, AssIGNoE T0 INmEENA'rIoNAI. com- BUSTION ENGINEERING CORBDRATION, A CORPORATION OF DELAWARE APPARATUS FOR PULVERIZED-FUEL BURNING Application filed November 30, 1923.

This invention relates to the burning of fuels, and is particularly useful in connection with the burning of pulverized coal under stationary boilers, in connection with which the invention will be described.

One of the primary objects of my invention is the provision of improved means for the prevention of slagging of the refuse of combustion and maintaining such refuse in a form in which it is readily removable, without detriment to the fire box or combustion chamber refractories.

Another object of the invention is to secure better and more effective combustion of the fuel by the obtaining of a more effective and thorough admixture of the fuel with the air needed to support combustion.

Still another object of the invention is to secure effective distribution of the air for combustion and its mixture with the fuel, in combustion chambers of relatively large size.

A further object of the invention is to burn the fuel and admit the air for combustion in such manner that supplemental means-such as water screens for the prevention of slagging of the refuse may be dispensed with. I

- How the foregoing, together with such other obiects as may hereinafter appear, or are incident to my invention, are obtained, is illustrated in the accompanying drawings wherein:

Fig. 1 is a transverse vertical section through Ia combustion chamber embodying my improvements, taken'on the line 11 of Fig.2;

Fig. 2 is a section taken on the line 22 of Fig. 1; A

Fig. 3 is a side elevation of a detail of my invention.

Referring now to the drawings I have illustrated a combustion chamber A which may be of much larger size than the present practice and suitable for relatively high capacity installations. This combustion chamber is relatively deep and increases somewhat in horizontal dimension, from the bottom upward. The pulverized coal is admitted through one or more burners 7 arranged to Serial No. 677,900.

discharge the fuelpreferably with a portion of the air needed for combustion, say for example, from'10 to 40% of the amount requiredin a downward direction through the top or arch 8 of the chamber, adjacent the front wall 9. The descending fuel stream is promptly ignited by the heat of the chamber and as it travels downwardly, it progressively meets with air supplied through the inlets 10 which are arranged in vertically spaced rows. The relative directions and the relative velocities of the entering fuel stream and the air admitted through the inlets 10 are such that a certain amount of 'eddying is set up which secures an intimate admixture of the fuel and the air so that each particle of fuel is surrounded by air and, in its traverse of the combustion space, is continually brought into contact with air which has not been impoverished of its oxygen.

The descending fuel and flame stream continues its downward course until its momentum is overcome by the draft, and the fuel and flame stream bends and reverts on itself in U-shape as indicated in Fig. 2.

The size of the combustion chamber is such that combustion is substantially completed before the ascending fuel and flame stream reaches the tubes 11, or other evap orating surfaces, located over the outlet 12 of the combustion chamber.

The wall'of the combustion chamber is made hollow and the space is divided into compartments by the septa or partitions 13, 14, 15, 16 and 17 The partition 13 separates the space in the rear wall into two compartments B and O. The partitions 14 and 15 provide a compartment D in each side wall, communicating with the space in the front wall above the partition 16 which divides the space in the front wall into two general compartments E and F. The partition 17- provides a lower compartment in the side walls G, communicating at the rear with the compartment C and at the front with the compartment F in the front wall. The compartments C and F extend to the bottom of the combustion chamber walls.

The compartment E is divided into smaller combustion chamber, some distance above f compartments by the partitions 16,..which sma ler compartments communicate at the ends with the compartments D in the side walls. Similarly thecompartment F is divided by the partition 16".,

Extending transversely of the bottom of the the floor thereof, area plurality of metallic conduits 18 communicatin at the ends with the compartments C and F and being open at the top. Refractory blocks19 are carried on the conduits 18 such blocks being provided with upwardly directed discharg'e passages or openings 2 Above and below the partition 13, the compartments B and C, respectively, are provided with a plurality of inlet openings 21 and 22 each governed by, a gate 23 such as indicated in Fig. 3;

The course of the air is as follows: The air entering through the inlets 21 passes into the compartment B and from thence into the compartments D in the side walls from which it flows into the compartment E in the front wall, entering the divisions of such general compartment at the ends where the same communicate with the side wall compartments. From the divisions of the compartment E the air flows into the combustion chamber through the inlets as indicated by the arrows in Fig. 1. The partitions 16 secure a substantially uniform distribution of the entering air through the inlets 10. If desired, the compartment' D may be further divided by the partition 24, in which event a portion of the air flowing through the compartment B will take the course indicated by the upper arrows in Fig. 2.

The air entering through the inlet 22 traverses the compartment C and divides, part goin through the side wall compartments G and rom thence into the front wall compartment F, and part flowing into the conduits 18 and through the blocks 19 into the interior of the combustion chamber, discharging in an upward direction beneath thefuel and flame stream. That portion which flows through the compartments Gr, after traversing the compartment F enters the combustion chamber through the inlets 10.

The air traversing the spaces within the walls of the combustion chamber is, of course, preheated by the absorption of heat from such walls and thus serves an important purpose inpreserving the life of the refractories. The furnace temperatures are also not unduly lowered.

As before indicated, from 10 to 40% of the air needed for combustion is preferably supplied through the burners with the entering coal and the balance of the air required for combustion is supplied through the inlets 10, 10, and 20. That portion of the air which enters in the upper regions of the combustion chamber-through the inlets 10 because it is admitted transversely to the paths of the descending fuel, sets up eddying and secures an intimate admixture of the entering fuel and air, supplying oxygen for those portions of the fuel which, because of their size, may be most readily and quickly burned. That portion of the air which is admitted through the inlets 10', generally speaking, travels along withthe fuel in a stream bordering the convex side of the fuel and flame stream, providing a body of air into which the heavier gravitating particles of fuel will pass and meet with oxygen for their combustion. The

air admitted through the passages 20 also serves this purpose and, in addition, has the efliect of holding up or lifting the zone of combustion well above the bottom of the combustion chamber. In this connection, however, the combustion chamber is of such size that the length of flame travel is still such that combustion is completed before the tubes 11 are reached.

The air admitted through the inlets -10 in the bottom of the combustion chamber through which the gravitating refuse particles must pass as they leave the fuel and flame stream and by which such particles are cooled below the fusing or coalescingpoint, so that the refuse particles are deposited in flocculent or sand-like form, readily susceptible of removal through the gates 25 in the bottom of the combustion chamber. The cooling of. the walls at the bottom also helps in this regard. v

A portion.of the air admitted through the blocks 19and, to some extent also,a portion of the air admitted through the inlets 10 travels upwardly alon the rear wall intermediate the fuel and. ame stream and such wall.

The fuel is, therefore, burned in space and while thereis sufiicient eddying to secure the degree of admixture necessary to secure effective and complete combustion, nevertheless it is not so violent nor is the fueladmitted so forcibly that impingement of the fuel and flame stream occurs on any of the refractories. The cooling of the walls of the combustion chamber, particularly the rear wall, minimizes the scouring effect of the refuse particles tangentially discharged from the fuel and flame stream, as a protective coating of refuse builds up.

Theoretically a given quantity of air is required to burn a given quantity of coal, but practically an excess over the theoretical amount of air is required. Heretofore, the I is objectionable as it cuts down the eflicien'cy obtainable. By my arrangement the cooling zone is created without the admission of such a large excess of air and, therefore, the furnace may be operated with greater efiiciency and economy.

In some cases it may be desirable to use forced draft instead of natural draft, particularly with large combustion chambers, and in such case I provide a fan 26 supplying air under pressure to the conduit or casing 27, secured over the inlets 21 and 22 With the arrangement of airdistribution and control thereof described, forced draft may be employed Without encountering operating difficulties.

The supply of air through the inlets 10, 10' and 20 may be independently controlledby properly manipulating the dampers 23 affording great flexibility in meeting operating conditions.

-The passages 20 are preferably in the form of slots discharging fiat streams or sheetsof air which expand or mushroomiunder the heat providing a body of air below the fuel and flame stream, substantially coextensive with the bottom portion of the chamber in horizontal dimensions. The beneficial effect of this in relation to the cooling zone will be clear. It also promotes} admixture-of the fuel-particularly the gaseous portionswith the air. Q

Iclaimr I 1 1. In'combination with a pulverized fuel furnace having a burner delivering'the fuel downwardly adjacent one wall and an ofl'take in an upper part so that, in burning, the products 'of combustion must take a U-shaped course through the furnace chamber; a plurality ofvertically spaced conduits in the furnace: walls extending around the chamber, inlets from said conduits to the chamber in the wall adjacent the incoming'fuel stream, air admission ports extending from withoutthe furnace into the said conduits in the wall opposite said first-mentioned};. wall, valve means for the admission ports of said conduits'separately regulable as between the con-, duits, a plurality of substantially horizontally disposed air-conduits in the bottom of the chamber having upwardly-directed slot-like openings therein, and a communicating air'- channel from the lowermost airconduit in the furnace walls to said air conduits in the bottom of the chamber. I

2. In combination with a pulverized fuel furnace having a'burner delivering the fuel downwardly adjacent one Wall and an oiftake in an upper part so that, in burning, the products of combustion must take a U-shaped course throu h the furnace chamber; a plu-- rality of vert cally spaced conduits in the furnace walls extending around the chamber, inlets from said conduits to the chamber in the wall adjacent the incomingfuel stream, air

walls to said air-conduits in the bottom of the chamber, a common source of air-supply.to the said separately regulable, valve means, and an auxiliary source of air-supply to the said conduits in the bottom of the chamber.

' 3. Apulverized fuel burning furnace in- *cluding, in combination, a wall structure forming a chamber and having circumjacent air conduits, means for admitting fuel downwardly in the chamber forburning in sus ension, outlet means in an upper region 0 the chamber, inlets from said air conduits into the chamber, a plurality of conduits disposed transversely of the furnace adjacent its bot-, tom each having a longitudinal slit directed upwardly, and air conducting means interconnecting a wall conduit and said transverse conduits, together with air delivery means to said conduits.

4. A pulverized fuel burning furnace including, in combination, a wall structure forming a chamber and having circumjacent I air conduits, means for admittlng fuel down wardly in the chamber for burning in'suspension, outlet means in an upper legion of the chamber, inlets from saidair conduits-into the chamber, a plurality of conduits disposed transversely of thefurnace adjacent its bottonreach having a longitudinalslit directed upwardly,;and air conducting means interconnecting a wall conduit and said transverse conduits, together with means for delivering air under pressure to said conduits.

5. In a furnace for burning pulverized fuel, a combustion chamber, means for admitting pulverized fuel downwardly thereinto, and air conducting means having spaced slot-like inlets extending across the bottom portion of the chamber for admitting air in an upward direction beneath the-fuel and flame stream.

6. In a furnace for burning pulverized fuel,-a combustion chamber, means for admitting pulverized fuel downwardly thereinto,

air conducting means having spaced slot-like inlets extending across the bottom portion of the chamber for admitting air in an upward direction beneath the fuel and flame stream and means for admitting a stream of air to "EDWIN LU'NDGREN. 

